C.S.
Every restaurant on the strip should be serving Thanksgiving dinner, however, it may be pricey.
I found this on the web http://www.opentable.com/promo.aspx?pid=1&m=10. It looks like most of the restaurants are in the strip hotels. Buca Di Peppo shows two $$, which I would say will be close to $100. At that price, I don't suggest you get a glass of wine because you will blow the budget.
Fresh & Easy stores are now taking Thanksgiving dinner orders. I have never had their Turkey dinner, but most of their cooked foods are good. As well, the grocery stores often have a prepared Thanksgiving dinner that can be picked up. Our markets are Vons, Albertson's, and Smiths.
Most often the markets are open in the morning and close early. As far as chain restaurants, Vegas has a lot of the same restaurants as Arizona has.
You may also find a local casino to have shorter lines and be less expensive. Most of them are near a freeway exit, so they should be easy to access. Sam's Town, Station Casinos, and the Cannery's.
Best wishes.